The team behind controversial proposals for a £25bn Severn barrage have left MPs with unanswered questions about the cost to the taxpayer and ruled out building a major new port in Port Talbot.

Hafren Power, the company championing the constructing of an energy-generating barrage across the Severn estuary, corrected its written submission to Westminster’s Energy & Climate Change committee.

The company had pledged to consider “converting” a facility for construction caissons which it expects to be based in Port Talbot “into a port for ultra-large container ships.”

But during an appearance before the committee on Wednesday afternoon, Hafren Power chief executive Anthony Pryor said: “I think we used the wrong tense. We used the first-person rather than the third-person and we said we will consider building a ULC port at Port Talbot.

“That is not the case. We should have used the third-person and said it could be considered by somebody...

“We have no plans to build a new port at Port Talbot.”

The company’s executives came under sustained pressure from the committee to provide detail about the guaranteed payment for electricity – the “net strike price” it is seeking from the UK Government.

Chairman Gregory Shenkman said: “We are not terribly keen to discuss that today specifically. But we are seeking a price that will make the project viable within the [UK Government] levy control framework.

“And we expect the strike price we will be able to negotiate will fall below offshore wind and we hope close to or perhaps at the sort of strike price nuclear power is currently negotiating.”

Conservative committee chairman Tim Yeo stressed that the project must deliver the biggest savings in carbon emissions at the best value for the taxpayer to get the backing of MPs.

He said: “If there are technologies which deliver the same savings in terms of carbon emissions at much lower cost it would become very hard to justify recommending a commitment of the length and scale you are seeking.”

Mr Shenkman said that across the 120-year-plus lifetime of the barrage it could produce energy at approximately £48 per megawatt hour, compared with a rate of £88 for a nuclear power station over 60 years.

Mr Yeo said the forecasts contained an element of “jam tomorrow”.

Addressing fears about the impact on wildlife, Mr Shenkman said: “From the outset the barrage which we are proposing has been conceived and designed around the environmental concerns.

He claimed complaints were focussed on an earlier proposal for a barrage – not the one put forward by Hafren Power.

He said: “They were complaints about a scheme which would be ebb-only, with a small number of turbines involving damming. We propose none of these things.

“Our proposal is very different. It is more efficient and much, much more environmentally friendly.”

Mr Yeo responded: “I have to say, I think if you are frustrated by the fact people have criticised a scheme which is not precisely the one you are promoting that may be partly because the details of your own scheme have remained quite obscure to a lot of outsiders so far.”

The project is not due to be completed until 2025 but when asked how it could contribute to the goal of a 20% cut in emissions by 2020, Mr Shenkman said: “We believe that the EU will be prepared to take into account when looking at that target projects that are under construction.”

Chief executive Mr Pryor said the project was at a stage when it had not “started the environmental impact assessment or the economic impact assessments”.

Cardiff University professor of water management Roger Falconer, a member of Hafren Power’s expert panel, also appeared before the committee.

He said: “I believe, having looked at the estuary over some considerable period of time, that the potential power you get from the barrage is significantly bigger than you get from any other combination integrated over the estuary as a whole.”